Method of foaming a milled precursor

ABSTRACT

A method of making a foamed article comprises (a) milling a block or sheet of thermoplastic polymer to form a precursor; (b) crosslinking the thermoplastic polymer; (c) heating the precursor to a first temperature to soften the thermoplastic polymer; (d) infusing the thermoplastic polymer with at least one inert gas at a first pressure that is sufficient to cause the at least one inert gas to permeate into the softened thermoplastic polymer; and (e) while the thermoplastic polymer is softened, reducing the pressure to a second pressure below the first pressure to at least partially foam the precursor into a foamed article, wherein the foamed article is substantially the same shape as the precursor.

RELATED APPLICATION DATA

This Application: (a) is a continuation application of U.S. patentapplication Ser. No. 14/964,886, filed Dec. 10, 2015, which application(b) claims the benefit of U.S. Provisional Appln. No. 62/248,824, filedOct. 30, 2015. Each of U.S. patent application Ser. No. 14/964,886 andU.S. Provisional Appln. No. 62/248,824 is hereby incorporated byreference in its entirety.

FIELD

The present disclosure relates to methods for forming flexible foams andarticles made by the methods.

INTRODUCTION

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Flexible foams are used for cushioning, support, and to absorb impacts,for example in seats and furniture, footwear, packaging, straps,protective gear, and so on. In general, foam materials are made insheets or blocks and cut to a desired pre-form shape, then finished to afinal shape.

Foamed midsoles for athletic footwear may be made from crosslinkedpoly(ethylene co-vinyl acetate) (EVA), for example, which may be cutfrom a block or sheet of foam. Injection molding may typically not beused because foam materials made by this method must have higherspecific gravities to foam uniformly. A new mold in each size must bemade to injection mold a foamed midsole of a new design.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 shows a flow diagram for making a foamed article according to anembodiment of the present invention.

FIG. 2 shows a flow diagram for making a foamed article according to anembodiment of the present invention.

FIG. 3 shows a flow diagram for making a foamed article with an insertaccording to an embodiment of the present invention.

DESCRIPTION

A method of making a foamed article, for example a foamed component foran article or footwear, comprises milling or cutting a block of unfoamedthermoplastic polymer to form a precursor. The precursor may be made bymilling a block of unfoamed thermoplastic polymer material to a desiredshape. In some embodiments, the block is milled by a computerizednumeric control. The unfoamed thermoplastic polymer may be athermoplastic elastomer composition. The precursor is foamed into afoamed article. The unfoamed precursor may be substantially the sameshape as the foamed article, albeit with a smaller volume.“Substantially” is used here to indicate minor shape changes that occurduring the foaming process. For example, when foaming, the precursor maylose some definition around edges, corners or other features. Forexample, when foaming, the precursor may lose some definition aroundedges, corners or other features. For example, a 90° corner of theprecursor may not be as sharp in a foamed article because the corner maybecome slightly rounded during the foaming process. In some embodiments,the precursor is at least 20%, 30%, 40%, 50%, 60%, or 70% of the volumeof the foamed article. In other embodiments, the volume of the precursoris up to 30%, 40%, 50%, 60%, 70%, or 80% the volume of the foamedarticle. The precursor and foamed article may be in the shape of amidsole for an article of footwear. The thermoplastic polymer of theprecursor may be crosslinked before or after the precursor is foamed. Tofoam the precursor, the precursor is heated to a first temperature tosoften the thermoplastic polymer, and then the softened precursor isinfused with at least one inert gas at a first pressure. The firstpressure may be greater than atmospheric pressure. The temperature towhich the thermoplastic polymer is heated is sufficient to soften thethermoplastic polymer. The first pressure is sufficient to cause the atleast one inert gas to permeate into the softened thermoplastic polymer,forming infused softened thermoplastic polymer. The inert gas may be anoble gas, nitrogen, carbon dioxide, or any combination thereof. Theamount of the at least one inert gas infused into the softenedthermoplastic polymer members is sufficient to produce at least partialfoaming of the softened thermoplastic polymer in a subsequent step inwhich the infused softened thermoplastic polymer is exposed to a lowerpressure. After being infused with the inert gas, the thermoplasticpolymer can optionally be cooled to a second temperature, and thepressure reduced to atmospheric pressure (e.g., without foaming thethermoplastic polymer), then later heated again to foam the precursorand form the foamed article. The foamed article, for example a foamedcomponent for an article or footwear, can be again heated to atemperature at which the thermoplastic polymer softens to at leastpartially foam the thermoplastic polymer. The foamed article can beheated under pressure (for example at a pressure greater thanatmospheric pressure) to the temperature at which the thermoplasticpolymer softens and foamed with a reduction of the pressure, for examplea reduction to atmospheric pressure.

“Block” is used in this description to refer to a solid portion largerthan the precursor. The block may be, for example, a sheet, chunk,cuboid, or other solid, i.e. unfoamed, portion of the thermoplasticpolymer.

The foamed article, for example a foamed component for an article offootwear, can be again heated to a temperature at which thethermoplastic polymer softens to at least partially foam thethermoplastic polymer. The foamed article can be heated to a temperatureat which the thermoplastic polymer softens under pressure (for exampleat a pressure greater than atmospheric pressure) and foamed with areduction of the pressure, for example a reduction to atmosphericpressure.

A method of making a foamed article, for example a foamed component foran article of footwear, comprises milling a block of unfoamedthermoplastic polymer to form a precursor that contains a cavity. Theprecursor may be milled using a computerized numeric control. The blockmay be milled into a precursor for a foamed midsole. Before or followingmilling, the thermoplastic polymer may be crosslinked. An insertcomprising thermoplastic polymer may then be placed in the cavity of theprecursor. In some embodiments, insert is be printed into the cavityusing a three-dimensional (“3D”) printer. The precursor and insert arethen heated so that the thermoplastic polymer of each is infused with atleast one inert gas. The inert gas may be a noble gas, nitrogen, carbondioxide, or any combination thereof. The insert may also be infused withthe inert gas and foam at substantially the proportion as the precursor,or the insert may be of a material different from the precursor and mayfoam at a lesser or greater proportion as the precursor foams. Thethermoplastic polymer of the insert may be a thermoplastic elastomercomposition. Each of the insert and the precursor may independently beinfused with inert gas below or up to a saturation point. In otherwords, each of the insert and the precursor may independently be infusedwith the inert gas at a concentration below the saturation point or atthe saturation point. The precursor containing the insert is heated to afirst temperature to soften the thermoplastic polymer of the precursorand the thermoplastic polymer of the insert and allow the precursor andthe insert to at least partially foam. The thermoplastic polymer may beheated to the first temperature at a first pressure greater thanatmospheric pressure, then the pressure may be reduced to a secondpressure less than the first pressure to allow the thermoplastic polymerto at least partially foam.

An at least partially foamed article may be subjected to a secondfoaming step by heating the at least partially foamed article to asecond temperature at which the thermoplastic polymer is softened andinfusing the softened thermoplastic polymer with at least one inert gasat a third pressure that is sufficient to cause the at least one inertgas to permeate into the softened thermoplastic polymer, and thenreducing the pressure to fourth pressure below the second pressure tofurther foam the thermoplastic polymer. The third pressure may begreater than atmospheric pressure. The second temperature may be thesame as or different from the first temperature. The at least one inertgas used in the second foaming step may be the same as or different fromthe inert gas used in the original foaming step. Suitable examples ofthe inert gas are again noble gasses, nitrogen, carbon dioxide, or anycombination of these. The amount of inert gas infused into thethermoplastic polymer may be below or up to a saturation point. Thethird pressure is sufficient to cause the at least one inert gas topermeate into the softened thermoplastic polymer and can be the same asor different from the first pressure. The pressure is reduced to afourth pressure below the first pressure to further foam thethermoplastic polymer. The fourth pressure can be the same as ordifferent from the second pressure. The second foaming step can producea foamed article of a lower density. The second foaming step may also beused for further shaping the foamed article, for example when the secondfoaming step is carried out in a mold or with a partial mold.

The foamed article may include an insert. The precursor may be milledsuch that the precursor contains a cavity. An insert may be placed inthe cavity. In some embodiments, the insert is printed into the cavityusing a 3D printer. The insert may comprise a thermoplastic polymer. Insome embodiments, the insert is the same material as the precursor. Theinsert may also be infused with the inert gas and foam at substantiallythe proportion as the precursor.

The foamed article may be incorporated as cushioning into otherarticles. As nonlimiting examples, the foamed article may be a foamedelement in footwear, such as a part of a footwear upper, such as afoamed element in a collar, a midsole or a part of a midsole, or anoutsole or a part of an outsole; foam padding in shinguards, shoulderpads, chest protectors, masks, helmets or other headgear, kneeprotectors, and other protective equipment; an element placed in anarticle of clothing between textile layers; or the foamed article may beused for other known padding applications for protection or comfort,such as for a pillow, cushion, or in an article or furniture. In variousembodiments, the foamed article is a midsole for an article of footwear.A midsole provides cushioning in the footwear. A midsole should bedurable but also preferably adds as little weight as possible to thefootwear while still cushioning to the desired degree. A midsole alsoshould be able to be bonded to an outsole, an upper, or any othercomponents (e.g., a shank, an airbag, or decorative components) inmaking an article of footwear.

As used in this description, “a,” “an,” “the,” “at least one,” and “oneor more” indicate interchangeably that at least one of the item ispresent; a plurality of such items may be present unless the contextunequivocally indicates otherwise. All numerical values of parameters(e.g., of quantities or conditions) in this specification, including theappended claims, are to be understood as being modified in all instancesby the term “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; approximately or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in thetechnological field with this ordinary meaning, then “about” as usedherein indicates at least variations that may arise from ordinarymethods of measuring and using such parameters. In addition, disclosureof ranges are to be understood as specifically disclosing all values andfurther divided ranges within the range. The terms “comprising,”“including,” and “having” are inclusive and therefore specify thepresence of stated features, steps, operations, elements, or components,but do not preclude the presence or addition of one or more otherfeatures, steps, operations, elements, or components. Orders of steps,processes, and operations may be altered when possible, and additionalor alternative steps may be employed. As used in this specification, theterm “or” includes any one and all combinations of the associated listeditems.

FIG. 1 shows a flow diagram for making a foamed article according to oneembodiment of the present invention. In the first step 110, a block ofthermoplastic polymer is milled to a desired shape to create aprecursor. Then, the polymer of the precursor is crosslinked in step120. In some embodiments, the polymer of the precursor is crosslinkedprior to milling. In one embodiment, the crosslinking is performed bysubjecting the precursor to electron beam radiation. In step 130, thearticle is then heated to a first temperature to soften the article andinfuse the article with an inert gas at a first pressure. The inert gasmay be a noble gas, nitrogen, carbon dioxide, or any combination ofthese. The first pressure is sufficient to cause the at least one inertgas to permeate into the softened thermoplastic polymer. The firstexposure is at a pressure and for a duration of time sufficient for anamount of the gas to permeate into the softened polymer to cause atleast partial foaming when the pressure is reduced. The amount of gasrequired may depend upon factors such as the surface area of theprecursor, the type of polymer, the pressure, and the temperature. Theinfusing step may be continued until the point of saturation of thethermoplastic polymer with the gas. The article is then cooled to asecond temperature in step 140. Finally in step 150, the pressure isdecreased to a second pressure less than the first temperature to inducefoaming. The second temperature is one at which the gas will notsignificantly foam the thermoplastic polymer in a desired length oftime. For example, the second temperature may be at or below about 30°C. The second pressure may be atmospheric pressure. The article is thenat least partially foamed. The precursor may optionally be heated to afoaming temperature during step 150. The foaming temperature is atemperature that aids in foaming the precursor. The foaming temperaturemay be greater than room temperature. The article is then at leastpartially foamed.

FIG. 2 shows a flow diagram for making a foamed article according toanother embodiment of the invention. First, in step 210 a precursor ismade by milling a block of thermoplastic polymer to a desired shape.Then the polymer is crosslinked in step 220. The precursor is nextheated to a first temperature to soften the precursor and infuse theprecursor with an inert gas at a first pressure in step 230. The inertgas may be a noble gas, nitrogen, carbon dioxide, or any combination ofthese. The first pressure is sufficient to cause the at least one inertgas to permeate into the softened thermoplastic polymer. The firstexposure is at a pressure and for a duration of time sufficient for anamount of the gas to permeate into the softened polymer to cause atleast partial foaming when the pressure is reduced. The amount of gasrequired may depend upon factors such as the surface area of theprecursor, the type of polymer, the pressure, and the temperature. Theinfusing step may be continued until the point of saturation of thethermoplastic polymer with the gas. The infused precursor is then cooledto a second temperature in step 240. Then, in step 250, the pressure isdecreased to a second pressure. In step 260, the precursor is heated toa third temperature while at a third pressure to at least partially foamthe precursor. While remaining at the third temperature, the pressure isdecreased to a fourth pressure to induce foaming (step 270).

FIG. 3 illustrates a method for making a foamed article with an insertaccording to an embodiment of the present invention. In step 310, ablock of thermoplastic polymer is milled into a precursor. The precursormay have cavities to allow for an insert to be placed into theprecursor. In some embodiments, the milling is performed by acomputerized numeric control (CNC) machine. Then, in step 320, thethermoplastic polymer is crosslinked. In some embodiments, thecrosslinking is completed using electron beam radiation. In step 330, aninsert is placed into a cavity of the precursor. The precursor maycontain one or more cavities for inserts to be included. In someembodiments, the insert is printed into the cavity. In furtherembodiments, the insert is printed into the cavity using athree-dimensional (“3D”) printer. Then, in step 340, the precursor andany inserts are heated to soften the precursor and insert, and then aninert gas is introduced to the precursor and insert at a first pressure.The inert gas may be a noble gas, nitrogen, carbon dioxide, or anycombination of these. The first pressure is sufficient to cause the atleast one inert gas to permeate into the softened thermoplastic polymer.The first exposure is at a pressure and for a duration of timesufficient for an amount of the gas to permeate into the softenedpolymer to cause at least partial foaming when the pressure is reduced.The amount of gas required may depend upon factors such as the surfacearea of the precursor, the type of polymer, the pressure, and thetemperature. The infusing step may be continued until the point ofsaturation of the thermoplastic polymer with the gas. In step 350, theprecursor and insert are cooled to a second temperature. Finally, instep 360, the pressure is reduced to atmospheric pressure to foam theprecursor and insert. In some embodiments, the precursor may undergoadditional foaming steps.

The precursor for the foamed article is milled from a block ofthermoplastic polymer. The milling may be performed by a computerizednumeric control (“CNC”) machine. Using a CNC machine to prepare theprecursor creates a shaped precursor which may be foamed to provide afull-size foamed article. Milling an article after foaming may causescorching of the material. Milling a block of thermoplastic polymerbefore foaming may also allow for controlling the edges and corners ofthe precursors, allowing for a non-defective final part normally causedby curling or other expansion limitations. CNC milling of an unfoamedprecursor may also allow for the capture of scrap material for recyclingand reuse, and does not require building a mold. The milled precursor isin a desired shape that is substantially the same shape as the foamedarticle. In some embodiments, the precursor has a smaller volume thanthe volume of the foamed article. In some embodiments, the precursor maybe shaped like a midsole for an article of footwear. Once the precursoris foamed to full-size, the foamed article may be suitable for use as amidsole for an article of footwear. In other embodiments, the foamedarticle may be a footwear upper, footwear collar, footwear tongue,footwear insole, shinguard, shoulder pads, chest protector, mask,helmet, headgear, knee protector, article of clothing, strap, furniturecushion, or bicycle seat.

Partial molds, having a surface that limits foam expansion in at leastone direction but less than all directions, may optionally be usedduring the foaming step to further control the shape of the final part,for example to maintain a flat face or sharp edge. A partial mold doesnot fully enclose the article during foaming. As the article is notfully enclosed during the foaming, the infused gas present in thearticle is able to escape from at least a portion of an outer surface ofthe article, and from the partial mold. The partial mold may be adjacentto the article before foaming begins or the article may come intocontact with a surface of the partial mold during foaming to prevent thearticle from expanding further during foaming in the direction of thesurface of the partial mold. The surface of the partial mold that limitsfoam expansion may be flat and may optionally include one or more spacesthrough which the structure can expand beyond the surface duringfoaming. The outer surfaces of the article before the foaming may definea top, a bottom opposite the structure top, and an outer circumferencebetween the top and the bottom, and the surface of the partial mold maylimit foam expansion of at least a part of the outer circumference. Thesurface of the partial mold may limit foam expansion to expansion indirections of the top or the bottom or both the top and the bottom. Inanother example, the partial mold may have a bottom surface and a sidesurface or side surfaces that limit foam expansion and may be open in adirection opposite the bottom surface. The partial mold may include abottom portion and a side portion, and the side portion may or may notcompletely surround the article being foamed. The partial mold may haveadjacent sections that separate during foaming of the precursor to formthe foamed article. For example, the partial mold may have a first moldpart comprising the bottom surface and a second mold part comprising theside surfaces, wherein the first and second mold parts are adjacent butnot conjoined, in which case the second mold part may be moved away fromthe first mold part before unmolding the foamed article from the secondmold part.

In any of these examples, the partial mold may have a surface thatimparts a pattern or decoration on at least a portion of the foamedarticle. In any of these examples, the partial mold may have a shape ofa midsole for footwear. The shape may be that of a perimeter of amidsole or a part of a perimeter of a midsole. In any of these examples,the partial mold may be of a sacrificial nature that is destroyed inremoving the molded, foamed article. For example, the partial mold or aportion of the partial mold may be cut away or torn away after thearticle is molded. In another example, the partial mold or a portion ofthe partial mold may be melted or dissolved after the article is molded.In yet another example, the partial mold or a portion of the partialmold may become a part of the foamed article, for example the partialmold or a portion of the partial mold may be may become a layer orcomponent of a midsole for footwear that is foamed and shaped by thepartial mold. In such instances, the partial mold or a portion of thepartial mold may be adhesively attached or physically attached duringthe foaming and molding process.

The thermoplastic polymeric composition can include any thermoplasticpolymer, including thermoplastic elastomers that are suitable for theintended use of the foamed article to be made. Nonlimiting examples ofsuitable thermoplastic polymers and elastomers include thermoplasticpolyurethane elastomers, thermoplastic polyurea elastomers,thermoplastic polyamide elastomers (PEBA or polyether block polyamides),thermoplastic polyester elastomers, metallocene-catalyzed blockcopolymers of ethylene and α-olefins having 4 to about 8 carbon atoms,and styrene block copolymer elastomers such aspoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene), andpoly(styrene-isoprene-styrene), and poly(ethylene co-vinyl acetate)(EVA).

Ethylene may also be copolymerized with vinyl acetate to make ethylenevinyl acetate copolymer. The vinyl acetate content of the copolymer mayrange from about 5 or 10 wt % up to about 40 or 45 wt % of the polymerweight.

Thermoplastic polyurethane elastomers may be selected from thermoplasticpolyester-polyurethanes, polyether-polyurethanes, andpolycarbonate-polyurethanes, including, without limitation,polyurethanes polymerized using as polymeric diol reactants polyethersand polyesters including polycaprolactone polyesters. These polymericdiol-based polyurethanes are prepared by reaction of a polymeric diol(polyester diol, polyether diol, polycaprolactone diol,polytetrahydrofuran diol, or polycarbonate diol), one or morepolyisocyanates, and, optionally, one or more chain extension compounds.Preferably the polymeric diol-based polyurethane is substantially linear(i.e., substantially all of the reactants are difunctional).Diisocyanates used in making the polyurethane elastomers may be aromaticor aliphatic, and examples include, without limitation, isophoronediisocyanate (IPDI), methylene bis-4-cyclohexyl isocyanate (H12MDI),cyclohexyl diisocyanate (CHDI), m-tetramethyl xylene diisocyanate(m-TMXDI), p-tetramethyl xylene diisocyanate (p-TMXDI), 4,4′-methylenediphenyl diisocyanate (MDI, also known as 4,4′-diphenylmethanediisocyanate), 2,4- or 2,6-toluene diisocyanate (TDI), ethylenediisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane,1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI), 1,4-butylenediisocyanate, and the like, which may be used in combinations. Chainextension compounds, or extenders, have two functional groups reactivewith isocyanate groups, for example, diols, dithiols, diamines, orcompounds having a mixture of hydroxyl, thiol, and amine groups, such asalkanolamines, aminoalkyl mercaptans, and hydroxyalkyl mercaptans, amongothers. The molecular weight of the chain extenders may range from about60 to about 400. Alcohols and amines are typically used. Examples ofuseful diols include ethylene glycol and lower oligomers of ethyleneglycol including diethylene glycol, triethylene glycol and tetraethyleneglycol; propylene glycol and lower oligomers of propylene glycolincluding dipropylene glycol, tripropylene glycol and tetrapropyleneglycol; cyclohexanedimethanol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol,1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,3-propanediol,butylene glycol, neopentyl glycol, and combinations of these. Suitablediamine extenders include, without limitation, ethylene diamine,diethylene triamine, triethylene tetraamine, and combinations of these.Other typical chain extenders are amino alcohols such as ethanolamine,propanolamine, butanolamine, and combinations of these.

The polyester diols used in forming a thermoplastic polyurethaneelastomer are in general prepared by the condensation polymerization ofone or more polyacid compounds and one or more polyol compounds.Preferably, the polyacid compounds and polyol compounds aredifunctional, i.e., diacid compounds and diols are used to preparesubstantially linear polyester diols, although minor amounts ofmono-functional, tri-functional, and higher functionality materials(perhaps up to 5 mole percent) can be included to provide a slightlybranched, but uncrosslinked polyester polyol component. Suitabledicarboxylic acids include, without limitation, glutaric acid, succinicacid, malonic acid, oxalic acid, phthalic acid, hexahydrophthalic acid,adipic acid, maleic acid, suberic acid, azelaic acid, dodecanedioicacid, their anhydrides and polymerizable esters (e.g., methyl esters)and acid halides (e.g., acid chlorides), and mixtures of these. Suitablepolyols include those already mentioned, especially the diols. Inpreferred embodiments, the carboxylic acid component includes one ormore of adipic acid, suberic acid, azelaic acid, phthalic acid,dodecanedioic acid, or maleic acid (or the anhydrides or polymerizableesters of these) and the diol component includes one or more of includes1,4-butanediol, 1,6-hexanediol, 2,3-butanediol, or diethylene glycol.Typical catalysts for the esterification polymerization are protonicacids, Lewis acids, titanium alkoxides, and dialkyltin oxides.Polylactones, such as polycaprolactone diol, may also be used.

A polymeric polyether may be obtained by reacting a diol initiator,e.g., 1,3-propanediol or ethylene or propylene glycol, with alkyleneoxide chain-extension reagent. Polyethylene oxide (also calledpolyethylene glycol), polypropylene oxide (also called polypropyleneglycol), and block polyethylene oxide-polypropylene oxide copolymers maybe used. Two or more different alkylene oxide monomers may be randomlycopolymerized by coincidental addition or polymerized in blocks bysequential addition. Tetrahydrofuran may be polymerized by a cationicring-opening reaction initiated by formation of a tertiary oxonium ion.Polytetrahydrofuran is also known as polytetramethylene ether glycol(PTMEG).

Aliphatic polycarbonate diols that may be used in making a thermoplasticpolyurethane elastomer are prepared by the reaction of diols withdialkyl carbonates (such as diethyl carbonate), diphenyl carbonate, ordioxolanones (such as cyclic carbonates having five- and six-memberrings) in the presence of catalysts like alkali metal, tin catalysts, ortitanium compounds. Useful diols include, without limitation, any ofthose already mentioned. Aromatic polycarbonates are usually preparedfrom reaction of bisphenols, e.g., bisphenol A, with phosgene ordiphenyl carbonate.

The polymeric diol preferably has a weight average molecular weight ofat least about 500, more preferably at least about 1000, and even morepreferably at least about 1800 and a weight average molecular weight ofup to about 10,000, but polymeric diols having weight average molecularweights of up to about 5000, especially up to about 4000, may also bepreferred. The polymeric diol advantageously has a weight averagemolecular weight in the range from about 500 to about 10,000, preferablyfrom about 1000 to about 5000, and more preferably from about 1500 toabout 4000. The weight average molecular weights may be determined byASTM D-4274. The polymeric diol segments typically are from about 35% toabout 65% by weight of the polyurethane polymer, and preferably fromabout 35% to about 50% by weight of the polyurethane polymer.

Suitable thermoplastic polyurea elastomers may be prepared by reactionof one or more polymeric diamines with one or more of thepolyisocyanates already mentioned and one or more of the diamineextenders already mentioned. Polymeric diamines include polyoxyethylenediamines, polyoxypropylene diamines, poly(oxyethylene-oxypropylene)diamines, and poly(tetramethylene ether) diamines.

Suitable thermoplastic polyamide elastomers may be obtained by: (1)polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipicacid, sebacic acid, terephthalic acid, isophthalic acid,1,4-cyclohexanedicarboxylic acid, or any of the other dicarboxylic acidsalready mentioned with (b) a diamine, such as ethylenediamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, ordecamethylenediamine, 1,4-cyclohexanediamine, m-xylylenediamine, or anyof the other diamines already mentioned; (2) a ring-openingpolymerization of a cyclic lactam, such as ε-caprolactam orω-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine to prepare a carboxylicacid-functional polyamide block, followed by reaction with a polymericether diol (polyoxyalkylene glycol) such as any of those alreadymentioned. Polymerization may be carried out, for example, attemperatures of from about 180° C. to about 300° C. Specific examples ofsuitable polyamide blocks include NYLON 6, NYLON 66, NYLON 610, NYLON11, NYLON 12, copolymerized NYLON, NYLON MXD6, and NYLON 46.

Thermoplastic polyester elastomers have blocks of monomer units with lowchain length that form the crystalline regions and blocks of softeningsegments with monomer units having relatively higher chain lengths.Thermoplastic polyester elastomers are commercially available under thetradename HYTREL from DuPont.

Metallocene-catalyzed block copolymers of ethylene and α-olefins having4 to about 8 carbon atoms are prepared by single-site metallocenecatalysis of ethylene with a softening comonomer such as hexane-1 oroctene-1, for example in a high pressure process in the presence of acatalyst system comprising a cyclopentadienyl-transition metal compoundand an alumoxane. Octene-1 is a preferred comonomer to use. Thesematerials are commercially available from ExxonMobil under the tradenameExact and from the Dow Chemical Company under the tradename Engage™.

Styrene block copolymer elastomers such aspoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene), andpoly(styrene-isoprene-styrene) may be prepared may anionicpolymerization in which the polymer segments are produced sequentially,first by reaction of an alkyl-lithium initiator with styrene, thencontinuing polymerization by adding the alkene monomer, then completingpolymerization by again adding styrene. S-EB-S and S-EP-S blockcopolymers are produced by hydrogenation of S-B-S and S-I-S blockcopolymers, respectively.

In some embodiments, the thermoplastic polymer is crosslinked beforefoaming. The method of crosslinking may vary based on the thermoplasticpolymer used in the method. In some embodiments, the thermoplasticpolymer is crosslinked using radiation, such as ultraviolet (UV)radiation or electron beam radiation. For example, the thermoplasticpolymer may be crosslinked after the precursor is formed.

The precursor is infused with an inert gas by heating the thermoplasticpolymer to a first temperature soften the thermoplastic polymer andinfusing the softened thermoplastic polymer with at least one inert gasat a first pressure greater than atmospheric pressure that is sufficientto cause the at least one inert gas to permeate into the softenedthermoplastic polymer. The inert gas may be a noble gas, nitrogen,carbon dioxide, or any combination of these. The first pressure issufficient to cause the at least one inert gas to permeate into thesoftened thermoplastic polymer. The first exposure is at a pressure andfor a duration of time sufficient for an amount of the gas to permeateinto the softened polymer to cause at least partial foaming when thepressure is reduced. The amount of gas required may depend upon factorssuch as the surface area of the precursor, the type of polymer, thepressure, and the temperature. The infusing step may be continued untilthe point of saturation of the thermoplastic polymer with the gas.

The precursor having the thermoplastic polymer infused with the inertgas may then be cooled to a second temperature. The second temperatureis one at which the gas will not significantly foam the thermoplasticpolymer in a desired length of time. For example, the second temperaturemay be at or below about 30° C. Then, the pressure is reduced to asecond pressure. The second pressure may be atmospheric pressure. Theprecursor then is foamable. The precursor can be removed from thepressure vessel and transferred to another location, for example to amold in the same building or manufacturing site or transferred to aremote site, before it is foamed. The precursor is then foamed byheating the thermoplastic polymer at a third pressure to a thirdtemperature to soften the thermoplastic polymer to cause thethermoplastic polymer to at least partially foam the thermoplasticpolymer. The third temperature may be the same as or different from thefirst temperature at which the thermoplastic polymer was infused withthe inert gas. Once the third temperature is reached, the pressure isreduced to a fourth pressure or released (returned to atmospherictemperature) to cause the thermoplastic polymer to foam.

The precursor having the thermoplastic polymer infused with the inertgas may instead be foamed immediately without interim cooling or movingor transferring to a different position, piece of equipment, location,or geographic site. Once the softened thermoplastic polymer has beeninfused with the at least one inert gas, the pressure is reduced to asecond pressure below the first pressure to at least partially foam thethermoplastic polymer. The thermoplastic polymer remains softened whilefoaming. For example, the second pressure may be atmospheric pressure.

When the precursor is foaming, expansion of the precursor in one or morebut less than all directions may be constrained, for example by placingthe article with the precursor of thermoplastic polymer adjacent to orin direct contact with an unyielding surface, such as a partial mold asalready described. The foaming precursor may partially conform to theunyielding surface as it presses during foaming against the surface,expanding in unconstrained directions.

The foamable thermoplastic polymer may be foamed a second time byrepeating the process. The at least partially foamed, thermoplasticpolymer is heated to a second temperature to soften the thermoplasticpolymer and the softened thermoplastic polymer is again infused with atleast one inert gas at a third pressure that is sufficient to cause theat least one inert gas to permeate into the softened thermoplasticpolymer, then the pressure is reduced to a fourth pressure below thethird pressure while the thermoplastic polymer is softened to furtherfoam the thermoplastic polymer. The third pressure may be greater thanatmospheric pressure. The second temperature may be the same as ordifferent from the first temperature at which the thermoplastic polymerwas softened and infused during the original foaming process. The inertgas used in the second foaming process may be the same as or differentfrom the inert gas used to originally at least partially foam thethermoplastic polymer. Thus, the inert gas may be a noble gas, nitrogen,carbon dioxide, or any combination of these. The amount of inert gasinfused into the thermoplastic polymer may be up to a saturation point.The third pressure may be the same as or different from the firstpressure used in the original infusing step process, so long as it issufficient to cause the at least one inert gas to permeate into thesoftened thermoplastic polymer. The pressure can be reduced to a fourthpressure while the thermoplastic polymer is softened to allow thethermoplastic polymer to further foam. The fourth pressure may beatmospheric pressure.

The foamed article may be substantially the same shape as the precursor,though the foamed article may have an increased volume with respect tothe precursor. In some embodiments, the precursor is at least 20% or atleast 30% or at least 40% or at least 50% or at least 60% or at least or70% of the volume of the foamed article. In other embodiments, thevolume of the precursor is up to 30% or up to 40% or up to 50% or up to60% or up to 70% or up to 80% of the volume of the foamed article. Forexample, in various embodiments the precursor may be at least 20% and upto 80% of the volume of the foamed article or the precursor may be atleast 20% and up to 70% of the volume of the foamed article or theprecursor may be at least 20% and up to 60% of the volume of the foamedarticle or the precursor may be at least 20% and up to 50% of the volumeof the foamed article or the precursor may be at least 30% and up to 80%of the volume of the foamed article or the precursor may be at least 30%and up to 70% of the volume of the foamed article or the precursor maybe at least 30% and up to 60% of the volume of the foamed article or theprecursor may be at least 30% and up to 50% of the volume of the foamedarticle or the precursor may be at least 40% and up to 80% of the volumeof the foamed article or the precursor may be at least 40% and up to 70%of the volume of the foamed article or the precursor may be at least 40%and up to 60% of the volume of the foamed article or the precursor maybe at least 40% and up to 50% of the volume of the foamed article.

The precursor may be molded such that the precursor contains a cavity ora plurality of cavities. An insert may then be inserted into the cavityor cavities prior to foaming. The insert may be printed into thecavities using a 3D printer. The insert may be polymeric and may befoamed along with the precursor. The insert may comprise the samethermoplastic polymer as the precursor comprises or may comprise asecond thermoplastic polymer different from the thermoplastic polymer ofthe precursor. The insert may be infused with the inert gas while theprecursor is being infused with the inert gas. The insert may then foamsubstantially the same amount in proportion to the precursor, or theinsert may foam a different amount proportionally than the precursor.The insert may provide aesthetic details or structural support to thefoamed article.

In some embodiments an insert is printed onto the precursor using a 3Dprinter. Any suitable 3D printer may be used in the method for printingan insert onto the precursor. An example of a suitable printer may befound, for example, in U.S. Pat. No. 9,005,710, the subject matter ofwhich is herein incorporated by reference. The 3D printer may be used toprint a three dimensional insert onto the precursor, or in a cavity ofthe precursor. The insert may be the same or a different polymericmaterial as the precursor. In some embodiments, the insert is infusedwith the inert gas similarly to the precursor. In further embodiments,the insert foams an amount that is proportional to the precursor.

Among the foamed articles that may be made in this way are footwearuppers, footwear collars, footwear tongues, footwear insoles, footwearmidsoles, shinguards, shoulder pads, chest protectors, masks, helmets,headgear, knee protectors, articles of clothing, straps, furniturecushions, and bicycle seats.

In various embodiments, the foamed articles may be used as inserts in afurther molding process, such as in a thermoforming process, or may beattached by adhesives, fasteners, thermally welded, or otherwise tofurther articles.

The foregoing description of particular embodiments illustrate featuresof the invention, but the invention is not limited to any of thespecific embodiments that have been described. The features describedfor particular embodiments are interchangeable and can be used together,even if not specifically shown or described. The same may also be variedin many ways. The invention broadly includes such variations andmodifications.

What is claimed is:
 1. A method of making a foamed article, comprising:a) milling a block of a first thermoplastic polymer to form a precursorhaving a cavity; b) crosslinking the first thermoplastic polymer; c)placing an insert comprising a second thermoplastic polymer in thecavity of the precursor; d) heating the precursor and the insert in thecavity of the precursor to a first temperature to soften the precursorand the insert; e) infusing the precursor and the insert in the cavityof the precursor with a first inert gas under a first pressure; f)cooling the precursor and the insert to a second temperature below thefirst temperature; and g) reducing pressure to a second pressure lowerthan the first pressure to foam the precursor and the insert in thecavity of the precursor into a foamed article.
 2. The method accordingto claim 1, wherein the first inert gas includes one or more ofnitrogen, carbon dioxide, or a noble gas.
 3. The method according toclaim 1, wherein the milling is performed by computerized numericcontrol.
 4. The method according to claim 1, wherein the foamed articleis a footwear midsole.
 5. The method according to claim 1, wherein thefoamed article is a member selected from the group consisting of: afootwear upper, a footwear collar, a footwear tongue, and a footwearinsole.
 6. The method according to claim 1, further comprising: heatingthe foamed article to a third temperature to soften the foamed articleand form a softened foamed article; infusing the softened foamed articlewith a second inert gas at a third pressure sufficient to cause thesecond inert gas to permeate into the softened foamed article; andreducing pressure to a fourth pressure below the third pressure tofurther foam the softened foamed article.
 7. The method according toclaim 1, wherein the milling step includes milling multiple cavities inthe block of the first thermoplastic polymer, and wherein the placingstep includes placing multiple inserts into the cavities formed in theblock.
 8. The method according to claim 1, wherein the firstthermoplastic polymer is a first thermoplastic elastomer composition,and wherein the second thermoplastic polymer is a second thermoplasticelastomer composition.
 9. A method of making a foamed article,comprising: a) milling a block of a first thermoplastic polymer to forma precursor having a cavity; b) crosslinking the first thermoplasticpolymer; c) heating the precursor to a first temperature to soften theprecursor; d) infusing the precursor with a first inert gas under afirst pressure; e) infusing an insert formed of a second thermoplasticpolymer with a second inert gas, wherein the step of infusing the insertis conducted independent of the step of infusing the precursor; f)placing the insert in the cavity of the precursor; and g) heating theprecursor and the insert in the cavity of the precursor to a temperaturesufficient to soften the precursor and the insert and to at leastpartially foam the precursor and the insert and form a foamed article.10. The method according to claim 9, wherein the first thermoplasticpolymer is a different material than the second thermoplastic polymer.11. The method according to claim 9, wherein in the step of heating theprecursor and the insert in the cavity of the precursor foams theprecursor in a different amount proportionally than the insert isfoamed.
 12. The method according to claim 9, wherein the milling stepincludes milling multiple cavities in the block of the firstthermoplastic polymer, and wherein the placing step includes placingmultiple inserts into the cavities formed in the block.
 13. The methodaccording to claim 9, wherein the foamed article is a footwear midsole.14. The method according to claim 9, wherein the foamed article is amember selected from the group consisting of: a footwear upper, afootwear collar, a footwear tongue, and a footwear insole.
 15. A methodof making a foamed article selected from the group consisting of: afootwear midsole, a part of a footwear midsole, a footwear upper, afootwear collar, a footwear tongue, and a footwear insole, comprising:a) milling a block of a first thermoplastic polymer to form a precursorin a shape selected from the group consisting of: a footwear midsole, apart of a footwear midsole, a footwear upper, a footwear collar, afootwear tongue, and a footwear insole; b) crosslinking the firstthermoplastic polymer; c) heating the precursor to a first temperatureto soften the precursor; d) infusing the precursor with a first inertgas under a first pressure; e) cooling the precursor to a secondtemperature below the first temperature; f) reducing pressure to asecond pressure lower than the first pressure; g) heating the precursorto a third temperature while at a third pressure to partially foam theprecursor and form a partially foamed article; and h) decreasingpressure to a fourth pressure lower than the third pressure to furtherinduce foaming to form the foamed article, wherein the foamed article isa member selected from the group consisting of: a footwear midsole, apart of a footwear midsole, a footwear upper, a footwear collar, afootwear tongue, and a footwear insole, and wherein a volume of theprecursor is at least 20% and up to 80% of a volume of the foamedarticle.
 16. The method according to claim 15, further comprising:moving the precursor from a first location to a second location afterthe pressure is reduced to the second pressure and before the precursoris heated to the third temperature.
 17. The method according to claim16, wherein the second location is a mold or a partial mold.
 18. Themethod according to claim 15, wherein the milling is performed bycomputerized numeric control.
 19. The method according to claim 15,wherein the foamed article is a footwear midsole.
 20. The methodaccording to claim 15, wherein the foamed article is a member selectedfrom the group consisting of: a footwear upper, a footwear collar, afootwear tongue, and a footwear insole.